Lecture Twelve--ICS 131--Fall 00--2 Nov 2000

Review of lecture 11--Computers and Health Care

Great (if not greatest) Need

Potential for great good, great harm
Need to control cost
Potential ease of applications ???
Progress to date is modest

Why hasn't more been done?

If money, spend it on devices
Other (overwhelming) problems in health care
Privacy concerns
Need to change system, e.g., preventative care

Software Safety


Shiver, Jube, Jr. FAA Software Flaw Spotlights Malady of Digital Age,

LA Times, 27 Oct 00, C1, C10

Leveson, Nancy, and Turner, Clark S. An investigation of the Therac-25 Accidents, IEEE Computer, July 1993, 18-41. [Use Google to get to Leveson, Nancy web page]

1. Software in critical applications

    One thing to have problems in productivity software

    Quite another to have problems in software controlling life-critical applications

2. Two examples

    A. Air traffic control

"The glitch in Palmdale that delayed air traffic
is blamed on coding and on insufficient testing and controller training."

"A lone air traffic controller, sitting in the darkened confines of the
    Palmdale Air Route Traffic Control Center,
    innocently shut down much of the air traffic across
    the Southwest last week be merely typing a a
    few too many characters on his computer."

entered 9 characters to represent a Mexican flight

system could only handle five characters

    inadequate testing,
inadequate training on new system
inadequate training on old system

aggravated by shift problems

Software customized for each air hub


B. Therac 25

A device used to provide radiation treatment
for cancer patients

Six cases where the device malfunctioned and
provided significant overdoses of radiation
causing deaths and injuries

Problems--four contributing factors

•Management inadequacies and lack of procedures

for following through on all reported incidents

•overconfidence in the software and

removal of hardware interlocks

(making the sofware into a single point of failure

that could lead to an accident)

•presumably less-than-acceptable

software-engineering practices

•unrealistic risk assessment along with overconfidence

in the results of these assessments.


3. What can be done?

a. Who's at fault?

b. Understanding "accident"

"Most accidents are system accidents; that is, they stem from complex interactions between various components and activities. To attribute a single cause to an accident is usually a serious mistake. In this article, we hope to demonstrate the complex nature of accidents and the need to investigate all aspects of system development and operation to understand what has happened and to prevent future accidents." page 1

c. Don't trust software, i.e., rely solely on the software

d. The interface issue

e. System engineering issues

f. Sofware engineering issues

"documentation should not be an afterthought

software quality assurance practices and standards should be established

designs should be kept simple

ways to get information about errors--for example software audit trails-- should be designed into the software from the beginning

the software whould be subjected to extensive testing and formal analysis

at the module and software level; system testing alone is not adequate"

g. Role of government


review, testing

h. Role of educational institutions


Readings for 7 Nov 00

Dunham, Kemba J. Telecommuter' lament. WSJ, 31 Oct 00, B1, B18

Hafner, Katie. Working at home today?, NY Times, 2 Nov 00, D1, D8

Optional readings

Microsoft Break in, e.g., Schwartz, John. Irregular new accounts alerted Microsoft to network intruder, NY Times 29 Oct 00, A25

Schmitt, Eric. Budget deal stumbles ontiming of worker-safety provision, NY Times, 1 Nov 00, A23

Cohen, Randy. Pushing the e-envelope, NY Times Magazine, 29 Oct 00, 26

Flanigan, James. Value shifts from hardware to service. LA Times, 29 Oct 00, C1, C4

Harmon, Amy. Napster users mourn end of free music. NY Times, 1 Nov 00, C1, C4

Richtel, Matt, and Kirkpatrick, David D. Internet service to charge a fee for music rights, NY Times, 1 Nov 00, A1, C4

Miller, Greg, and Dunn, Ashley. Internet's toll on social life? no cause for worry, study says, LA Times, 26 Oct 00, C1, C10

Iritani, Evelyn. Sites Cast Net to Bring Asian Women Online. LA Times, 30 Oct 00, C1, C5.

Deutsch, Claudia H. Bricks-and-clicks world needs commercial space, NY Times, 30 Oct 00, C1, C5

Kuczynski, Alex. Magazines mining web for readers, NY Times, 30 Oct 00, C1, C16